true - Logical 1 (true) - MATLAB (original) (raw)

Syntax

Description

true is shorthand for the logical value 1.

[T](#bt7dazv-1-T) = true([n](#bt7dazv-1-n)) is an n-by-n matrix of logical ones.

[T](#bt7dazv-1-T) = true([sz](#bt7dazv-1-sz)) is an array of logical ones where the size vector, sz, defines size(T). For example, true([2 3]) returns a 2-by-3 array of logical ones.

example

[T](#bt7dazv-1-T) = true([sz1,...,szN](#bt7dazv-1-sz1szN)) is a sz1-by-...-by-szN array of logical ones where sz1,...,szN indicates the size of each dimension. For example, true(2,3) returns a 2-by-3 array of logical ones.

example

[T](#bt7dazv-1-T) = true(___,like=[p](#bt7dazv-1-p)) returns an array of logical ones of the same sparsity as the logical variablep using any of the previous size syntaxes.

example

Examples

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Use true to generate a 3-by-3 square matrix of logical ones.

A = 3×3 logical array

1 1 1 1 1 1 1 1 1

The result is of class logical.

Use true to generate a 3-by-2-by-2 matrix of logical ones.

ans = 3×2×2 logical array ans(:,:,1) =

1 1 1 1 1 1

ans(:,:,2) =

1 1 1 1 1 1

Alternatively, you can use a size vector to specify the size of the matrix.

ans = 3×2×2 logical array ans(:,:,1) =

1 1 1 1 1 1

ans(:,:,2) =

1 1 1 1 1 1

Note that specifying multiple vector inputs returns an error.

true along with false can be used to execute logic statements.

Test the logical statement

~(A and B) = (~A) or (~B)

for A = true and B = false.

~~(true & false) == (~~true) | (~false)

The result is logical 1 (true), since the logical statements on both sides of the equation are equivalent. This logical statement is an instance of De Morgan's Law.

Generate a logical array of the same sparsity as the selected array.

A = logical(sparse(5,3)); whos A

Name Size Bytes Class Attributes

A 5x3 41 logical sparse

T = true(4,like=A); whos T

Name Size Bytes Class Attributes

T 4x4 184 logical sparse

The output array T has the same sparse attribute and data-type as the specified array A.

Input Arguments

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Size of square matrix, specified as an integer. n sets the output array size to n-by-n. For example, true(3) returns a 3-by-3 array of logical ones.

If n is 0, then T is an empty matrix.
If n is negative, then it is treated as 0.

Size vector, specified as a row vector of integers. For example, true([2 3]) returns a 2-by-3 array of logical ones.

If the size of any dimension is 0, then T is an empty array.
If the size of any dimension is negative, then it is treated as 0.
If any trailing dimensions greater than 2 have a size of 1, then the output, T, does not include those dimensions.

Size inputs, specified by a comma-separated list of integers. For example, true(2,3) returns a 2-by-3 array of logical ones.

If the size of any dimension is 0, then T is an empty array.
If the size of any dimension is negative, then it is treated as 0.
If any trailing dimensions greater than 2 have a size of 1, then the output, T, does not include those dimensions.

Prototype, specified as a logical variable.

Output Arguments

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Output of logical ones, returned as a scalar, vector, matrix, or N-D array.

Data Types: logical

Tips

true(n) is much faster and more memory efficient than logical(true(n)).

Extended Capabilities

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Usage notes and limitations:

Dimensions must be real, nonnegative, integers.

Usage notes and limitations:

Dimensions must be real, nonnegative, integers.

The true function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced before R2006a